Hiding a peppercorn with your invisibility cloak

It’s the first time I’ve heard of an invisibility cloak that can hide something visible to the naked eye.  A peppercorn may not sound like much but compared to cloaked objects that are usually measured at the nanoscale (nano means one billionth of a metre), this is a huge step forward. What makes this discovery even more interesting is that it’s simple and inexpensive compared to the other systems used to achieve invisibility. From the Jan. 25, 2011 news item on Nanowerk,

Unlike the other attempts to produce invisibility by constructing synthetic layered materials, the new method uses an ordinary, common mineral called calcite — a crystalline form of calcium carbonate, the main ingredient in seashells. “Very often, the obvious solution is just sitting there,” says MIT mechanical-engineering professor George Barbastathis, one of the new report’s co-authors.

The work is being done by a team of researchers from the Singapore-MIT Alliance for Research & Technology (SMART). From the SMART website,

Established in 2007, the SMART Centre is MIT’s first research centre outside of Cambridge, MA and its largest international research endeavor. The Centre is also the first entity in the Campus for Research Excellence and Technological Enterprise (CREATE) currently being developed by NRF.

Here’s how they created an invisibility cloak,

In the experiment reported in this paper, the system works in a very carefully controlled setting: The object to be hidden (a metal wedge in the experiment, or anything smaller than it) is placed on a flat, horizontal mirror, and a layer of calcite crystal — made up of two pieces with opposite crystal orientations, glued together — is placed on top of it. When illuminated by visible light and viewed from a certain direction, the object under the calcite layer “disappears,” and the observer sees the scene as if there was nothing at all on top of the mirror.

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